The present invention relates to a method and apparatus for manufacturing a semiconductor; and, more particularly, to a hydrogen annealing process and apparatus therefor for use in manufacturing semiconductor devices.
Al or Cu film has been used for the construction of wiring in a semiconductor device. If one or more oxygen molecules remain in the Al or Cu film, they may cause for the fine wiring to be prematurely aged, thereby resulting in short-circuiting. Accordingly, the Al or Cu film on a substrate requires deoxidization by using, e.g., a hydrogen annealing process.
Al film is widely used for wiring in semiconductor devices due to its low cost and excellent fabricability. Since Al itself, however, has relatively high conductor resistance, the wiring with Cu or Cu alloy is more preferred for fabricating a faster processing unit. However, since Cu is easily oxidized, the hydrogen annealing process becomes even more important in case of Cu or Cu alloy wiring.
Japanese Patent Laid-open Publication No. 5-291268 discloses a conventional hydrogen annealing apparatus, operable at an atmospheric pressure. As shown in FIG. 5, a reaction chamber 2 is embedded in a reaction furnace 1, and a boat 3 is loaded or unloaded within the reaction chamber 2. A hydrogen gas introduction line 4 and a vacuum evacuation line 5 are coupled to the reaction chamber 2, wherein the vacuum evacuation line 5 is connected through a valve 6 to a vacuum evacuation device 7. An upstream of the vacuum evacuation line 5 is coupled with a hydrogen combustion pipe 9 through a valve 8, wherein the hydrogen combustion pipe 9 is coupled with a combustion chamber 10 and an end of the hydrogen combustion pipe 9 is equipped with a combustion nozzle 11. A hydrogen ignition line 12 is also coupled with the combustion chamber 10, wherein one end of the hydrogen ignition line 12 is introduced to a vicinity of the combustion nozzle 11 and fired with a pilot burner. An exhaust duct 13 is also coupled with the combustion chamber 10 and an exhaust device (not shown) is connected to the exhaust duct 13. The combustion chamber 10 includes a damper 14 for allowing the inside of the combustion chamber 10 to be vented out to the atmosphere.
In carrying out the hydrogen annealing process using the apparatus, the valve 6 is turned open so that the air in the reaction chamber 2 is evacuated by the vacuum evacuation device 7 and, then, the valve 6 is closed. Hydrogen gas is introduced, under the atmospheric pressure, through the hydrogen gas introduction line 4 to the reaction chamber 2 to perform the hydrogen annealing process and, then, a valve 8 is turned open.
The reacted hydrogen gas is evacuated to the combustion chamber 10. The hydrogen gas released through the hydrogen combustion pipe 9 from the combustion nozzle 11 is fired by the pilot burner for exhaustion in the combustion chamber 10. Since the released hydrogen gas is burned in the combustion chamber 10, the exhaust gas released from the exhaust duct 13 may have no hydrogen gas left or at a level lower than a predetermined value.
A primary object of the hydrogen annealing process is to deoxidize the metal film of Al or Cu, i.e., to remove oxygen molecules off the metal film. Another object is to remove impurities in the metal film, in particular, in the Cu film, to enhance the electrical property thereof. Still another object is to enhance the adhesive property between the Cu film and its underneath layer.
An atmospheric annealing process may be preferable for deoxidizing the metal film, for example, as in a deoxidization process for multilayer wirings.
In order to enhance the electrical property or the adhesive property with the underneath layer a depressurized annealing process at, e.g., about 50 Torr may be preferable.
For example, an etching process, prior to the hydrogen annealing process, may leave impurities and additives attached on the film which have an adverse impact on the characteristics of the device. Since most of the impurities and additives have low vapor pressure, they may be preferably removed in a depressurized state. Through the hydrogen annealing process, the impurities are replaced with hydrogen atoms, so that binding between the metal film and its underneath layer can be enhanced, which in turn results in a higher adhesive property therebetween. In other words, the hydrogen annealing process in a depressurized state may attain not only the deoxidization of the metal film but also better electrical and adhesive properties with the underneath layer. Therefore, the choice between the atmospheric annealing process and the depressurized process may vary with the objective of the annealing process.
Unfortunately, however, the conventional hydrogen annealing apparatus can perform the hydrogen annealing process at an atmospheric process but not at a depressurized condition for the following reasons.
As explained above, the hydrogen gas in the combustion chamber 10 must be burned at the atmospheric pressure in the conventional hydrogen annealing apparatus; and, if the reaction chamber is to be operated in a depressurized state, the gas stream may reflux from the combustion chamber to the reaction chamber. As a result, the hydrogen gas, which is left unused or unreacted, can react with the oxygen gas introduced into the reaction chamber, thereby causing an explosion. The fire from a pilot burner for burning the hydrogen gas may ignite the explosion. Owing to such difficulties, therefore, there has continued to exist a need for a hydrogen annealing apparatus operable at a low pressure.
It is, therefore, an object of the present invention to provide a method and apparatus capable of performing a depressurized hydrogen annealing process safely.
It is another object of the present invention to provide a method and apparatus capable of performing a depressurized hydrogen annealing process as well as an atmospheric hydrogen annealing process to reduce the equipment cost thereof.
In accordance with a preferred embodiment of the present invention, there is provided a method capable of performing a hydrogen annealing process either at an atmospheric pressure or at a depressurized state in a hydrogen annealing apparatus, wherein the hydrogen annealing apparatus includes a reaction chamber, a hydrogen gas introduction line for feeding hydrogen gas into the reaction chamber and an atmospheric exhaust line and a depressurized exhaust line connected to the reaction chamber, comprising the step of:
Switching the atmospheric exhaust line and the depressurized exhaust line to selectively perform a depressurized hydrogen annealing process or an atmospheric annealing process.